From: William Chen (kwchen@netvigator.com)
Date: Wed Mar 17 2004 - 09:20:37 GMT-3
Dear all,
I have a scenario of multicast and want your guys' comment:
It is a hub-and-spoke frame-relay NBMA Network:
R2 ------- R1 ------ R3
And, it is full connectivity, that mean the spoke router no only have the map to the hub, but also a map to the other spoke router. That is:
! R2
int s0/0
encap frame
ip addr 172.16.123.2 255.255.255.0
no frame inverse-arp
frame map ip 172.16.123.1 201 broadcast
frame map ip 172.16.123.2 201
frame map ip 172.16.123.3 201 broadcast
!
Then, I have to configure multicast (PIM-DM) between R1 and R3, and there are clients connected to R3. Moverover, I have to source traffic from R2. I know that will cause a problem, because in R1 multicast traffic come from the interface S0/0, cannot be forwarded out of the same interface to R3. The solution can be create a tunnel between R2 and R3, and let the multicast traffic flows along the tunnel to R3.
My question is: since R2 have two frame-relay maps with broadcast, when it generates multicast traffic, it will send two copies of packets and forward it to R1 (pesudo-broadcast). Then R1 will get two copies of packets of every multicast packet and forward it to R3. I think it will not cause a big problem, but surely waste bandwidth.
If you have this question in real lab? What will you do? create another tunnel between R1 and R2?
Best Regards,
William Chen
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